General Graphics Tutorials -- Dithering |
Dithering
Dithering is the process that a program uses when it cannot display the full range of colors in a particular image. For example, if a gradient is to be displayed on a system that does not have the hardware needed to display all of the shades that make up the gradient (see figure 1.1) then the software may dither the image (see figure 1.2).
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| figure 1.1 |
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| figure 1.2 |
Figure 1.2 shows what the image looks like when it is necessary to dither the available colors to arrive at a set of colors that aren't available. What happens is that some of the colors are mixed in such a way as to "fake" the missing colors. An alternative to dithering is to use only the colors to which the software has access. This can result in banding, though (see figure 1.3).
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| figure 1.3 |
Neither of these alternatives is a nice solution to a common problem that plagues web designers.
There are other alternatives, though. You can use the JPG format on images with smooth transitions, such as gradients. You can use an optimal palette for GIF images and hope that people have the needed hardware to prevent your images from being dithered.
Pros and Cons:
One of the pros of dithering an image, using a web palette yourself, is that you'll know how the image will appear to all of the people visiting your site. One of the cons is that dithered images will actually make for larger GIFs than non-dithered images. The reason for this lies in how GIFs are compressed.
Be sure to check out some of our other general graphics tutorials.
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